Cathode for electronic discharge devices



Nov. 30, 1948. H.'B. ALLEN, JR

CATHODE FOR ELECTRONIC DISCHARGE DEVICES Filed Sept. 5, 1944 INVEIIVTOR. flown/did ZZQWJI' A TTOR/VEY Patented Nov. 30, 1948 CATHODE FOR ELECTRONIC DISCHARGE DEVICES Howard B. Allen, Jr., Chatham, N. J., assignor to National Union Radio Corporation, Newark, N. J., a corporation of Delaware Application September 5, 1944, Serial No. 552,721

2 Claims. 1

The present invention relates to reinforcing the cathode of an electron discharge device such as a radio tube.

In the manufacture of radio tubes the cathode, especially of the indirectly heated type, becomes very soft under heat used during bombarding and in the heater wire used to heat the cathode, causing it to bow or bend under its own weight in handling, particularly on rather long cathodes. This frequently results in cathode-to grid shorts and in abnormal plate current readings in cases where the bowing does not actually produce ashort.

It is an object of the present invention to reinforce the cathode to keep its straight and perpendicular during heat treatment so as to maintain proper relations between cathode and grid.

Another object is the provision of reinforcing means which does not materially cool the cathode during normal operation, thus resulting in lowering the efliciency thereof.

A specific object of the invention is the provision of a reinforcing rib or ribs, preferably formed integrally with the cathode and running perpendicular thereof.

Other objects of the invention will manifest themselves as the description proceeds.

Referring to the accompanying drawings:

Fig. 1 is a perspective view of a cathode embodying the invention;

Fig. 2 is a similar view of a modified form of the invention; 7

Fig. 3 is an enlarged, fragmentary detail view showing the formation of the reinforcing ribs extending inwardly of the cathode; and I Fig. 4 is a similar view showing the ribs-folded against the adjacent side of the cathod from which they are formed.

It is common practice to make the shell or sleeveof an indirectly heated cathode of aj single piece of sheet metal, and for electrical purposes, the ends .of the sleeve are secured togetherin any suitablemanner, as for example by interlocking the edges. According to the present invention, the cathode l comprises a tubular shell or: sleeve 2 having the edges 3 thereof crimped together, the sleeve being generally rectangular in crosssection and of considerably greater length than width. Obviously the sleeve 2 may take any configuration, but it is characteristic of this type of cathode that the heater element (not shown) enclosed within the sleeve 2 may consist of a plurality of strands or sections. However, the heater construction is well known in the art and forms no part of the present invention.

To reinforce the cathode l, means such as a rib 4 is formed longitudinally of the sleeve 2. The rib 4 may take the form shown in Fig. 1 which has the appearance of an indentation or generally U-shaped shallow trough. This indentation is formed preferably centrally of one of the lateral sides of the sleeve 2 and care should be exercised that the rib 4 does not extend inwardly too far on account of interference with the heater element or possibility of shorting against the opposing surface of the sleeve.

A modification of the rib just described may take the form of longitudinal fins 5 (see Fig. 2) which are preferably evenly spaced and are an integral part of the sleeve. In cathode sleeves where the spacing of the lateral sides is relatively close, as an expedienc to conserve space and avoid interference with the heater element, the ribs 4 may be folded substantially against the adjacent side of the sleeve as shown in Fig. 4.

From the foregoing, it will be apparent that a characteristic feature of the presently constructed cathode sleeve is the formation of a reinforcing rib or ribs of such a character as not to interfere with the heater element by crowding the same within the space in which it is housed; secondly, to impart sufficient reinforcement to the sleeve, in order to insure the prevention of cathode-to-grid shorts, also abnormal plate currents, and the like.

Modifications of the present invention will suggest themselves to those skilled in the art, and it is intended to cover all such modifications as come within the scope of the appended claims.

What is claimed is:

1. A cathode sleeve for indirectly heated cathodes, comprising a tubular metal member, the exterior surface of which is to be coated with electron-emissive material and the interior of which is to receive a heater element, said tubular member being substantially rectangular in cross section and having one side wall corrugated inwardly with the adjacent corrugated surfaces in contact to provide inwardly extending rigid fins for increasing the mechanical rigidity of the 3 sleeve while maintaining the exterior surface of UNITED STATES PATENTS said wall substantially fiat. N

2. A cathode sleeve according to claim 1 in i gg i g which each of said fins is bent back along its 2032179 Lowry 1936 leagth to a position substantiallyparallel with 5 g Smith May 1938 Sam 2,119,913 Holst et a1 June 7, 1938 2,256,297 Smith et al Sept. 16, 1941 HOWARD ALLEN, 2,266,622 Green Dec. 16, 1941 REFERENCES CITED 10 FOREIGN PATENTS The following references are of recordovin the Number 1 .Country A a a 7 Date file of this patent: 814,265. France Feb. 24, 1946 

